QMI AGENCY

TransCanada has shut down a section of its Canadian Mainline natural gas pipeline system in Manitoba following an explosion early Saturday morning.

The blast, which sent a fireball into the sky, happened just after midnight local time Saturday in Otterburne, which is about 50 km south of Winnipeg

"We are in the process of venting natural gas from the system to eliminate the fuel source for the fire at a valve site approximately 25 km south of Winnipeg," Grady Semmens, a spokesman for the Calgary-based company, wrote in an email.

Semmens added that the fire is "steadily decreasing in size and is being closely monitored by TransCanada staff with support from local emergency response crews. There are no reported injuries at this time and our response efforts are proceeding safely. We will continue to take steps to protect the safety of the public and our employees."

Five homes in the area have been evacuated as a precaution, he said.

TransCanada says the cause of the fire is unknown and investigations can not begin until the fire has been put out.

Earlier this week, TransCanada began shipping crude oil through the southern part of its controversial Keystone XL pipeline.